Test composition and process for detecting organic polyhalogen compounds



United States Patent US. Cl. 23230 9 Claims ABSTRACT OF THE DISCLOSUREMethod and solid composition for detecting certain organic polyhalogencompounds in aqueous fluids consisting of the utilization of a testsystem comprising a solid acid addition salt of pyridine such aspyridine citrate or pyridine tartrate and a solid caustic material suchas caustic soda or caustic potash.

This invention relates to a method for the detection in aqueous liquids,of organic compounds containing chlorine, bromine or iodine, and tocompositions useful in such a method. The term halogen is used herein torefer collectively to chlorine, bromine and iodine.

The detection of bound halogen in aqueous liquids such as urine isfrequently of clinical importance. For example, workers who arehabitually exposed to chlorinated solvents, such as those used as drycleaning agents, paint removers, refrigerants, fire extinguishers,fumigants, anesthetics, and anthelmintics, are liable to absorb them intoxic quantity, and it is, therefore, important to be able to know whenthis has happened, e.g., by detecting the presence of such chlorinatedcompounds, or their metabolic produces, in the urine of such workers.For example,, trichloroethylene is widely used as a dry-cleaningsolvent, and cases of poisoning with this compound have been reported.It is excreted as trichloroacetic acid in the urine, and a convenientmethod for the detection of the latter substance in urine isconsequently desirable.

It is known that a red color is formed when halogenated organiccompounds such as chloroform, bromoform, or iodoform are heated withpyridine and caustic alkali in aqueous medium, and this color reactionhas been used for the detection of polyhalogen compounds includingtrichloroacetic acid. The test is applicable to a wide variety oforganic compounds containing two or more halogen atoms joined to asingle carbon atom and which in the presence of alkali are degraded to areactive carbene species, e.g., as follows:

C13CH OH 013C H 0130- :CClz C1" While this test is effective, it hasheretofore always required the use of liquid reagents and theapplication of external heat.

A simple method has now been discovered, using only solid reagents andfor which no external source of heat is necessary, by which it ispossible to detect the presence of halogen-containing compounds of theaforesaid type in aqueous liquids containing them. According to thepresent invention, a method for detecting the presence, in an aqueousliquid, of an organic halogen-containing compound comprises adding, to apredetermined quantity of the said liquid, a solid, preferablynon-hygroscopic, acid addition salt of a pyridine base unsubstituted inthe 2- and 4-positions, and either solid caustic soda or solid causticpotash, the weights and weight ratio of the said alkali and acidaddition salt being such that on admixture with the aforesaidpredetermined quantity of aqueous liquid,

Patented Oct. 14, 1969 the mixture heats spontaneously to at least aboutC. find a liquid pyridine base separates as a supernatant ayer.

It is apparent that the color produced is proportional to the amount ofpolyhalogen present and by the expediency of proper color standards, aquantitative as well as quanlitative test method may be achieved.

The invention also provides, solid anhydrous compositions for use in theaforesaid method.

In the new method, when the solid caustic alkali and the solid pyridinesalt are added to the aqueous liquid being tested, the alkali liberatesthe free pyridine base from the salt, and the heat of dissolution of thealkali in water, together with the heat of neutralization of any freeacid groups which may be present, causes the mixture to heat up. Sincepyridine bases are not very soluble in concentrated caustic alkalisolution, the base liberated floats on the surface of the aqueous liquidand is colored red if any appropriate halogen-containing compound ispresent in the aqueous liquid. Immediately after addition of the solidreagents, the mixture is shaken, e.g., for about half a minute, topromote dissolution of the solid reagents and then allowed to stand. Itis possible to devise formulations which, when added to a predeterminedamount of aqueous liquid, cause the liquid to boil, thus obviating anyneed for shaking. A positive test should be apparent in not more than 5minutes.

Sodium hydroxide is preferred to potassium hydroxide as it causes,weight for weight, a greater liberation of heat. The preferred pyridinebase is pyridine itself, and the preferred non-hygroscopic pyridine saltis pyridine citrate or tartrate, though other acid addition salts ofpyridine, e.g., pyridine oxalate, malonate, sulphosalicylate, maleate,fumarate, ketomalonate, sulphamate, phosphate, and hydrochloride, can beused if desired. The phosphate and hydrochloride being hygroscopic arenot preferred but can be used if desired. It will beunderstood, however,that the presence of hygroscopic salts in the compositions of theinvention gives rise to storage problems. Salts with acids which formvery insoluble sodium salts under the conditions of the test should beavoided, e.g., p-toluene-sulphonates, as the sodium salts of such acidsseparate so quickly from the strongly alkaline solution that thedissolution of the reactants is inhibited. Substituted pyridine saltswhich have been found effective in the present invention include3-methyl pyridine, 3-benzyl pyridine, 3,5-dibenzyl pyridine and thelike.

It is especially convenient to compress a mixture of the solid causticsoda or potash and the solid pyridine salt into tablets each containingthe correct quantity of reagent for use with a suitable small,predetermined, quantity of the aqueous liquid to be tested. For example,tablets may be made up weighing /2 to 1 gram each, suitable for reactionwith A1 to 1 cubic centimeter of urine. In the solid composition, theamount of caustic alkali must, of course, be more than sufficient toneutralize the acid in the pyridine salt and give a distinctly alkalinemixture. Generally, an amount of caustic alkali at least 50% greaterthan that necessary to neutralize the acid in the pyridine salt Will beused, i.e., at least 1 /2 moles of caustic present for each mole ofpyridine salt. The determination of appropriate quantities of thecaustic alkali and the pyridine salt for use in connection with apredetermined amount of aqueous liquid, e.g., 0.5 cc., presents nodifficulty and can readily be carried out by routine experiment. Thus asolution in water or the type of aqueous liquid for which the testmethod is likely to be employed, e.g., urine, of trichloroacetic acid orother substance known to react strongly in the test is prepared,suitably in a concentration of 15 mg. percent. To, e.g., 0.5 cc. of thissolution, varying amounts of the solid reagents, e.g.,

pyridine citrate and caustic soda, are added and the mixture shaken andthen allowed to stand, until a combination is formed which gives astrongly colored upper supernatant layer. Generally for 0.5 cc. of testliquid, the appropriate amount of caustic soda will be 0.25 to 0.5 g.and the appropriate amount of pyridine salt about 0.3 to 0.5 g. The useof larger proportions of solid reagents than this is liable to causesemi-solid mixtures to be formed in which color formation may be hard todetect. Smaller proportions, on the other hand, may give inadequateheating of the mixture so that no color formation occurs. However, asalready stated, appropriate proportions can readily be determined byroutine experiment.

When the solid compositions are made up in tablet form, they mayconveniently contain, in addition to the pyridine salt and causticalkali, additional substances to act as binding agents and/ordisintegrating agents. Such substances include citric acid, tartaricacid, boric acid, potassium peroxosulphate, and polyethylene glycol,e.g., of molecular weight greater than about 4000.

In use, such solid compositions are added to the aqueous liquid undertest, and the mixture is allowed to stand (without shaking if themixture boils spontaneously) for from /2 to 5 minutes, generally about 1minute. If the aqueous liquid contains an appropriate halogen-containingcompound, a pink or red color develops in the supernatant pyridinelayer. It has been found that the new method can give a readilydetectable red color with concentrations of trichloroacetic acid as lowas 0.004% by weight. As already made clear, it is important not to usetoo much or too little of the aqueous liquid under test in relation tothe amount of caustic alkali and pyridine salt added.

A suitable composition in accordance with the invention is as follows:

Parts by weight Pyridine citrate 349 Caustic soda 279 Potassiumperoxosulphate 43 Citric acid 19.1 Polyethylene glycol M. W. 6000 9.6

A tablet weighing about 0.7 g., made in the conventional manner from theabove ingredients in the indicated weight ratios has been found to worksatisfactorily. The citric acid may be replaced by tartaric acid, andthe polyethylene glycol by boric acid or magnesium trisilicate. One suchtablet is suitable for the treatment of about 0.5 ml. of aqueous liquid.The tablet is added to the aqueous liquid and the mixture allowed tostand. Ordinarily color will develop for a positive reaction in one-halfto one minute, but it is advisable to allow the mixture to stand forfive minutes if no red or orange color is produced, to ensure that thetest is negative.

The present invention will be further illustrated but not limited by thefollowing examples:

EXAMPLE 1 One-half (0.5) ml. of a urine sample containing mg.trichloroacetic acid per 100 ml. urine was placed in a test tube andabout 0.7 g. of pyridine citrate added thereto. About 0.5 g. (S pellets)of sodium hydroxide (caustic soda) was then added and the tube gentlyshaken. Heat evolved immediately and in about 15 seconds a color startedto develop. The tube was then allowed to stand and settle for about 30seconds during which time a redpurple pyridine layer separated andfloated on top of the test solutions. The color remained substantiallyunchanged overnight.

EXAMPLE 2 A test was carried out in the manner described in Example 1with the exception that pyridine hydrochloride was substituted forpyridine citrate. Because of the hygroscopic nature of the pyridine saltused the composition was prepared immediately prior to use. A clearred-purple color appeared in the supernatant pyridine layer as inExample 1.

4 EXAMPLE 3 A test was carried out as in Example 1 with the exceptionthat pyridine oxalate was substituted for pyridine citrate. A cloudy butperceptible red-purple color appeared in the supernatant pyridine layeras in Example 1.

EXAMPLE 4 A test Was carried out as in Example 1 with the exception that0.5 g. of pyridine tartrate and 0.4 g. of sodium hydroxide pellets wereused in place of the 0.7 g. pyridine citrate and the 0.5 g. sodiumhydroxide. The mixture was shaken for 60 seconds and after settling forseconds a clear red supernatant pyridine layer formed in the tube.

EXAMPLE 5 A test was carried out as in Example 1 except that 0.5 g. ofpyridine citrate and 0.9 g. of potassium hydroxide (caustic potash) wereused in place of the 0.7 g. pyridine citrate and the 0.5 g. sodiumhydroxide. The tube was shaken for 30 seconds and after settling for 3minutes a clear brownish-red supernatant pyridine layer formed in thetube.

EXAMPLE 6 A test was carried out as in Example 1 except that 3- methylpyridine citrate was used in place of the unsubstituted pyridinecitrate. The color yield was equivalent to that achieved in Example 1.

EXAMPLE 7 A test was carried out as in Example 4 except that ground(powdered) sodium hydroxide was used in place of the pellets. Aftersettling for 60 seconds a positive red supernatant pyridine layer formedin the tube.

EXAMPLES 8-15 In the following examples, the tests were carried outsubstantially as in Example 1 with the exception that 0.5 g. of pyridinecitrate and 0.4 g. of sodium hydroxide were used in place of the 0.7 g.pyridine citrate and the 0.5 g. sodium hydroxide. Table 1 gives thepolyhalogen being tested for, the concentration thereof in a watersolution and the resultant response color of the supernatant pyridinelayer.

TABLE 1 Cone.

(mg. Response Example Polyhalogen detected percent) color 82,2-diehloropropionie acid 14.0 Pale pink. 9 Chloral hydrate 23.2 Red.10 Chloroform (1) Red. Carbon tetrachloride.-. (2) Red. Bromoform (1)Red. Trichloroacetomtrlle (2) Red. Chloramphenicol. 20 Red-brown. 15Iodolorm (a) Do.

1 One drop of the polyhalogen added to ml. water. 2 Saturated aqueoussolution. 3 One crystal of the polyhalogen added to ml. water.

What is claimed is:

1. A test composition for the detection, in an aqueous liquid, of anorganic polyhalogen compound capable of forming a reactive carbenespecies which comprises a solid acid addition salt of a pyridine baseunsubstituted in the 2- and 4-positions and at least 1 moles of asubstance selected from the group consisting of solid caustic soda andsolid caustic potash for each mole of pyridine salt.

2. A test composition as in claim 1 wherein the solid acid addition saltof the pyridine base is selected from the group consisting of pyridinecitrate, pyridine tartrate, pyridine oxalate, pyridine malonate,pyridine sulfosalicylate, pyridine maleate, pyridine fumarate, pyridineketomalonate, pyridine sulfamate, pyridine phosphate and pyridinehydrochloride.

3. A test composition as in claim 1 wherein the solid acid addition saltof the pyridine base is pyridine citrate.

4. A test composition as in claim 1 wherein the solid acid addition saltof the pyridine base is pyridine tartrate.

5. A test composition as in claim 1 wherein the solid acid addition saltof the pyridine base is pyridine citrate and the caustic is causticsoda.

6. A test composition as in claim 1 wherein the polyhalogen compound istrichloroacetic acid.

7. A test composition as in claim 1 in the form of a compressed tablet.

8. A process as in claim 7 wherein the solid acid addition salt ofpyridine is pyridine citrate and the caustic is caustic soda.

9. A process for detecting, in an aqueous liquid, an organic polyhalogencompound capable of forming a reactive carbene species which comprisesadding to said aqueous liquid a test composition comprising a solid acidaddition salt of a pyridine base unsubstituted in the 2- and 4-positionsand a substance selected from the group consisting of solid caustic sodaand solid caustic potash, said References Cited FOREIGN PATENTS 2/1946Great Britain.

OTHER REFERENCES Seto et al.: Analytical Chemistry, vol. 28, pp. 1625-1629 (October 1956).

JOSEPH SCOVRONEK, Primary Examiner U.S. Cl. X.R. 2325 3; 252408

